Re: Synchronizing slots from primary to standby

On Fri, Dec 29, 2023 at 6:59 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Wed, Dec 27, 2023 at 7:43 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > >
> > > 3) The slotsync worker uses primary_conninfo but also uses a new GUC
> > > parameter, say slot_sync_dbname, to specify the database to connect.
> > > The slot_sync_dbname overwrites the dbname if primary_conninfo also
> > > specifies it. If both don't have a dbname, raise an error.
> > >
> >
> > Would the users prefer to provide a value for a separate GUC instead
> > of changing primary_conninfo? It is possible that we can have some
> > users prefer to use one GUC and others prefer a separate GUC but we
> > should add a new GUC if we are sure that is what users would prefer.
> > Also, even if have to consider this option, I think we can easily
> > later add a new GUC to provide a dbname in addition to having the
> > provision of giving it in primary_conninfo.
>
> I think having two separate GUCs is more flexible for example when
> users want to change the dbname to connect. It makes sense that the
> slotsync worker wants to use the same connection string as the
> walreceiver uses. But I guess today most primary_conninfo settings
> that are set manually or are generated by tools such as pg_basebackup
> don't have dbname. If we require a dbname in primary_conninfo, many
> tools will need to be changed. Once the connection string is
> generated, it would be tricky to change the dbname in it, as Shveta
> mentioned. The users will have to carefully select the database to
> connect when taking a base backup.
>

I see your point and agree that users need to be careful. I was trying
to compare it with other places like the conninfo used with a
subscription where no separate dbname needs to be provided. Now, here
the situation is not the same because the same conninfo is used for
different purposes (walreceiver doesn't require dbname (dbname is
ignored even if present) whereas slotsyncworker requires dbname). I
was just trying to see if we can avoid having a new GUC for this
purpose. Does anyone else have an opinion on this matter?

--
With Regards,
Amit Kapila.